Architecture of ballast with integrated rf interface

ABSTRACT

The invention is a new architecture for a high frequency (HF) ballast with wireless communication interface. The new architecture integrates the RF wireless interface into the ballast. A user control transmits an RF control signal to a second antenna at the ballast site which provides the RF signal to the ballast which activates the fluorescent lamp. The ballast includes a transceiver/receiver, a communication decoder, a power control stage and a power stage. The transceiver/receiver receives the RF signal and communicates it to the communication decoder which acts as an interface to the power stage control. The power stage control controls the power stage that activates the fluorescent lamp. The communication decoder, power control stage, power stage and transceiver/receiver are located within the ballast enclosure which is an important part of the invention. If the power stage control is digital it maybe combined with the communication decoder into one microprocessor or digital controller such as an ASIC. The communication decoder may be a serial interface. The transceiver/receiver is an RF integrated circuit. The ballast further includes an isolator to isolate the transceiver/receiver from the first antenna. The isolator may be capacitive.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a ballast architecture with wirelesscommunication for activating a fluorescent lamp. More specifically, theinvention relates to a ballast which includes a communication decoder, alamp driver and a transceiver/receiver within the ballast enclosure.

DESCRIPTION OF THE RELATED ART

[0003] Lighting control in an office or commercial building has gonethrough several stages. The traditional control approach uses a separatecontrol box outside the ballast, as shown in FIG. 1. The central controlmanagement for the whole building can also control the lighting throughthe network.

[0004] With the recent advancements in RF and semiconductor technology,wireless control is attracting more and more attention from people inthe lighting industry. Currently there are some wireless control systemsavailable in the market. A typical RF wireless control structure isshown in FIG. 2. As can be seen in the figure, the wires between thewall unit and the control box in FIG. 1 are replaced by a transmitterand receiver. This eliminates the vertical wiring and brings wirelessadvantages. However, the control box is still outside of the ballast.

[0005] An additional problem with prior art RF systems is isolation. Forsafety reasons, when the RF receiver/transceiver is wired to theballast, there has to be some interface for high voltage isolation. Thisadds cost and complexity to the whole system. FIG. 3 shows the problem.The current state of the art uses a transformer or opto-isolation. FIG.3 also shows the structure of the ballast. The digital decoder is usedto decode the control command coming from the control box, it can be amicroprocessor. The lamp driver consists of the power stage and thecontrol IC. The power stage includes the high voltage driver, protectioncircuits, power storage and filter elements. The state-of-the-art forthe control IC is the Alpha-based analog IC for controlling the powerstage. Reference for Alpha IC is U.S. Pat. Nos. 5,680,017 and 5,559,395.

[0006] The current approach of lighting control faces the followingchallenges:

[0007] 1. Cost: adding a separate box connected to the ballast increasesthe cost.

[0008] 2. Power savings: if the power consumption information can be fedback from ballasts, the central management can easily improve the energyutilization. However, with the analog ballast, it is not easy to build atwo-way communication link without extra cost.

[0009] 3. Resolving the high voltage isolation problem describedpreviously.

SUMMARY OF THE INVENTION

[0010] The invention is a new architecture for a high frequency (HF)ballast with wireless communication interface. The new architectureintegrates the RF wireless interface into the ballast. A user controltransmits an RF control signal to a second antenna at the ballast sitewhich provides the RF signal to the ballast which activates thefluorescent lamp. The ballast includes a transceiver/receiver, acommunication decoder, a power control stage and a power stage. Thetransceiver/receiver receives the RF signal and communicates it to thecommunication decoder which acts as an interface to the power stagecontrol. The power stage control controls the power stage that activatesthe fluorescent lamp. The communication decoder, power stage control(analog or digital), power stage and transceiver/receiver are locatedwithin the ballast enclosure which is an important part of theinvention. If the power stage control is digital it may be combined withthe communication decoder into one microprocessor. The communicationdecoder may be a serial interface. The transceiver/receiver is an RFintegrated circuit. The ballast further includes an isolator to isolatethe transceiver/receiver from the second antenna. The isolator may becapacitive.

DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a prior art traditional control approach using aseparate control box outside the ballast.

[0012]FIG. 2 shows a typical prior art RF wireless control structure.

[0013]FIG. 3 shows a prior art RF wireless system with isolation

[0014]FIG. 4 shows a new inventive architecture for high frequency (HF)digital ballast with wireless communication interface.

[0015]FIG. 4a shows a block diagram of the operation of the inventivearchitecture of FIG. 4

[0016]FIG. 5 shows a functional block diagram of a workingimplementation of the inventive ballast with an integrated RF interface.

[0017]FIG. 6 shows a detailed schematic diagram of the workingimplementation of FIG. 5.

[0018]FIG. 7 shows an embedded antenna on a printed circuit board.

[0019]FIG. 8 shows how RF signals travel through the plastic ballastcase and plastic light fixture cover.

[0020]FIG. 9 is a half wavelength slot antenna for a metal casedballast.

[0021]FIG. 10 is a functional block diagram of a handheld remote controlfor the inventive architecture of FIG. 4

DETAILED DESCRIPTION OF THE INVENTION

[0022]FIG. 1 is a prior art traditional control approach using aseparate control box outside the ballast. The control box 10 is wired toone or more ballasts 12. It is also connected with a wall unit 14 thatacts as a network interface to communicate with the central controlmanager for the whole building through the wired network 16 as shown inFIG. 1. The control box 10 normally has a microcontroller 18 with adigital to analog converter (DAC) 20 inside. It can turn on/off and dimthe ballast for fluorescent (TL) lamps. The central control managementfor the whole building can also control the lighting through thenetwork.

[0023] In FIG. 2, the wires between the wall unit 14 and the control box10 in FIG. 1 are replaced by a transmitter 24 and receiver 26, Thiseliminates the vertical wiring and brings wireless advantages. However,the control box 28 is still outside of ballast 12.

[0024]FIG. 3 shows an additional problem of isolation with current stateof the art RF wireless systems. For safety reasons, in FIG. 3 when thecontrol box 28 containing RF receiver 26 is wired to the ballast 30,there has to be some interface for high voltage isolation from lampdriver 34. The isolation comes from the use of a transformer oropto-isolation 32 as the signals go through the interface as lowfrequency digital signals. This adds cost and complexity to the wholesystem.

[0025]FIG. 4 shows a new inventive architecture for a high frequency(HF) ballast with wireless communication interface. RF signals aretransmitted from a user control 96 having a first antenna 97 to a secondantenna 112 in the new architecture. User control 96 may include a wallunit 98 and first antenna 97 or a handheld remote control 150 (FIG. 10).The new architecture integrates the RF wireless interface into theballast 100. The ballast consists of an isolator 102, atransceiver/receiver 104 which is an RF integrated circuit (IC), acommunication decoder 105 and a lamp driver 106. The lamp driverconsists of power stage 107 and power stage control IC 108. Thecommunication decoder 105 is digital. The power stage control IC 108 canbe a digital or analog IC. If a digital power stage control IC is used,the communication decoder 105 and the digital power stage control IC 108can be combined into one digital controller 110 such as a microprocessoror an ASIC. If the power stage control 108 is analog, then it isseparate from communication decoder 105. They may be on separate IC's orthey could be combined on a mixed signal ASIC. The communication decoder105 may be a serial interface. Digital controller 110 may be a digitalcontroller such as a, P6LV IC, developed at Philips Research USA inBriarcliff Manor, N.Y., or any other microcontroller that has therequired peripherals such as ADC and PWM, or the resources that allowthe users to build these peripherals by themselves. Second antenna 112needs to be isolated from the rest of the circuit, therefore, isolator102 provides isolation between second antenna 112 andtransceiver/receiver 104. Isolator 102 may be a capacitive network 116made up of a pair of capacitors. The isolation can be built with asimple capacitive network since the signals are at Radio Frequency. Inaddition, in the case that a plastic enclosure is used for a ballast andthe antenna does not have to stick outside of the ballast can, thisisolation can be avoided. This is in contrast to the previously referredto prior art where the transceiver/receiver is outside the ballast andis hardwired to the ballast. In that case there needs to be high voltageisolation between the ballast and the transceiver/receiver which addscomplexity and cost.

[0026] Transceiver/receiver 104 is used as a front end tomodulate/demodulate baseband signals. It interfaces with digitalcontroller 110, through communication decoder 105. Since communicationdecoder 105 and power stage control IC 108 (if digital) can be combinedinto one microprocessor instead of two separate microprocessors, thiseliminates any extra components. The P6LV IC is a 8051-based dedicatedmicrocontroller designed for lighting. It not only has the capability ofa standard 8051 microcontroller, but also the peripherals needed forcontrolling the lamp gear. Another alternative, the P8XC51microcontroller is also from the 8051 family. The baseband signalscoming out of the transceiver/receiver 104 are processed by the digitalcontroller IC 110 and provided to power stage 107 having a high voltageoutput to energize a fluorescent lamp.

[0027] The new architecture has the following features: All the modulesfor control are in one ballast box 118. No separate control box isneeded. This results in significant cost reduction. In addition, withwireless control, the cost of wiring is eliminated and makes it a muchbetter solution for retrofit market. Also because the communicationdecoder and power stage control (or digital controller 110) are in theballast, more control features can be implemented, such as binding agroup of lamps into one remote controller. The communication can also bemade bi-directional. The information on the lamp operation, such as thepower consumption, can be fed back in real-time. This leads to effectivepower utilization and savings. In addition, the isolation 102 can bebuilt with a simple capacitive network since the signals that go throughare high frequency. With the RF section 104 inside the ballast, theisolation interface can be much simplified.

[0028]FIG. 4a shows a block diagram of the operation of FIG. 4. Theoperational block diagram of FIG. 4a contains three sections: Radiotransceiver 104, microcontroller 110 and lamp driver 106. Radiotransceiver 104 receives/transmits data from second antenna 112 throughthe air interface. In the receiving mode, it passes the demodulated datato the microcontroller 110 for processing. In the transmitting mode, itmodulates the data from the microcontroller 110 and passes on the datato the second antenna 112 and the air interface. Microcontroller 110controls the radio and does the baseband processing. On top of thecommunication protocol, it also contains the application program thattells the ballast to operate the lamp in a certain way. The otherresponsibility for the microcontroller 110 is to control the lamp driver106, which drives the high voltage stage of the ballast. The highvoltage portion is directly connected to the lamps (not shown).

[0029]FIG. 5 shows a functional block diagram of the implementation of adigital addressable ballast with RF interface. It contains two boards,the main board 116 and the RF interface board 118. The main board 116contains the lamp driver 106 (from FIG. 4) which includes filter andrectifier 120, up-converter 122, half-bridge 124 and lamp currentdetection circuit 126. The output of half bridge rectifier 124 goes tofluorescent lamp 127. The interface board 118, HF-R digital module, iscomposed of RF transceiver 128, a microprocessor 130 and an EEPROM 132.

[0030]FIG. 6 shows the detailed schematic and block diagram of theimplementation of the interface between the RF transceiver 128 and theballast controller 130. As seen in the figure, U1(TR1001) is the radiotransceiver 128 by RF Monolithics, and IS2 (P8XC51-QFP) is themicrocontroller 130 by Philips Semiconductors which serves as theballast controller and controls the RF transceiver 128. The controlsignals from microcontroller 130 (pin 9, 10, 40, and 43) also go to thelamp driver 106 that is not shown in the figure. A memory 132 used formicrocontroller 130 is also shown. The antenna is set at ANT1 and ANT2that are connected to the R_IO pin of the transceiver (U1).

[0031] For the ballast with integrated RF interface, one important issueis how to get the radiation outside the ballast. There are several waysto design the antenna. FIG. 7 shows the embedded antenna 140, which is ametal trace put on the printed circuit board (PCB) 142. This worksbecause the RF signals go through the plastic case 144 of ballast 100and the plastic cover 144 of the light fixture, as shown in FIG. 8.Another option is a halfwavelength slot antenna 146 shown in FIG. 9.This is a solution for metal cased ballast.

[0032] The proposed ballast with RF interface can be used together witha handheld remote control in a wireless lighting control system. Thehandheld remote control should contain the same RF transceiver andcommunicate with the ballast using a wireless communication protocol thesame as user control 96 in FIG. 4. FIG. 10 shows the block diagram ofthe remote control 150. It consists of the RF transceiver 152, amicroprocessor 154 or other type of digital control IC, and a userinterface 156 such as key pads for user request in and certain type ofdisplay (e.g. LEDs) to give indications of the operating status.

[0033] While the preferred embodiments of the invention have been shownand described, numerous variations and alternative embodiments willoccur to those skilled in the art. Accordingly, it is intended that theinvention be limited only in terms of the appended claims.

I claim:
 1. An RF wireless architecture for activating a fluorescentlamp, the RF wireless architecture including a second antenna whichreceives an RF control signal and provides it to a ballast, the ballastcomprising, a power stage providing a high voltage signal to activatesaid fluorescent lamp, a power control stage for controlling said powerstage, a communication decoder acting as an interface to said powerstage control a transceiver/receiver receiving said RF control signaland providing said RF control signal to said communication decoder, saidcommunication decoder, said power stage control, said power stage andsaid transceiver/receiver located within said ballast.
 2. The apparatusof claim 1 in which said communication decoder is a serial interface. 3.The apparatus of claim 1 in which said transceiver/receiver is an RFintegrated circuit.
 4. The apparatus of claim 1 in which said ballastfurther includes an isolator circuit to isolate saidtransceiver/receiver from said second antenna.
 5. The apparatus of claim4 in which said isolator circuit is capacitive.
 6. The apparatus ofclaim 1 including a user control which transmits an RF control signalfrom a first antenna to said second antenna.
 7. An RF wirelessarchitecture for activating a fluorescent lamp, the RF wirelessarchitecture including a second antenna which receives an RF controlsignal and provides it to a ballast, the ballast comprising, a powerstage providing a high voltage signal to activate said fluorescent lamp,a digital controller for controlling said power stage, atransceiver/receiver receiving said RF control signal and providing saidRF control signal to said digital controller, said digital controller,said power stage and said transceiver/receiver located within saidballast.
 8. The apparatus of claim 7 in which said digital controllerhas a communication decoder and a digital power stage control, saidcommunication decoder communicating with said transceiver/receiver andacting as an interface to said power stage control.
 9. The apparatus ofclaim 8 in which said communication decoder is a serial interface. 10.The apparatus of claim 9 in which said transceiver/receiver is an RFintegrated circuit.
 11. The apparatus of claim 10 in which said ballastfurther includes an isolator circuit to isolate saidtransceiver/receiver from said second antenna.
 12. The apparatus ofclaim 11 in which said isolator circuit is capacitive.
 13. The apparatusof claim 7 including a user control which transmits an RF control signalfrom a first antenna to said second antenna.
 14. An RF wirelessarchitecture for activating a fluorescent lamp, the RF wirelessarchitecture including a second antenna which receives an RF controlsignal and provides it to a ballast the ballast comprising, a lampdriver for providing an activating signal to said fluorescent lamp, acommunication decoder, acting as an interface to said lamp driver, atransceiver/receiver communicating with said communication decoder forreceiving said RF control signal and providing said RF control signal tosaid communication decoder; said communication decoder, said lamp driverand said transceiver/receiver located within said ballast.
 15. The RFwireless architecture of claim 14 in which said lamp driver has a powerstage control and a power stage, said power stage control receiving theoutput of said communication decoder and providing a control signal tosaid power stage to activate said fluorescent lamp.
 16. The apparatus ofclaim 15 in which said communication decoder is a serial interface. 17.The apparatus of claim 15 in which said transceiver/receiver is an RFintegrated circuit.
 18. The apparatus of claim 15 in which said ballastfurther includes an isolator to isolate said transceiver/receiver fromsaid first antenna.
 19. The apparatus of claim 18 in which said isolatorcircuit is capacitive.
 20. The apparatus of claim 14 including a usercontrol which transmits an RF control signal from a first antenna tosaid second antenna.
 21. The apparatus of claim 6 in which saidcommunication decoder is a serial interface.
 22. The apparatus of claim6 in which said transceiver/receiver is an RF integrated circuit. 23.The apparatus of claim 6 in which said ballast further includes anisolator to isolate said transceiver/receiver from said second antenna.24. The apparatus of claim 23 in which said isolator circuit iscapacitive.
 25. The apparatus of claim 1 in which said RFtransceiver/receiver, said communication decoder, said power stagecontrol and said power stage are integrated into one single IC.
 26. Theapparatus of claim 8 in which said digital controller is integrated intoone single IC.